Evaluation of gaseous pollutants arising from slurry containing recycled plasterboard

With the rise in prices of traditional bedding material, farmers are considering alternatives including gypsum from recycled plasterboard. Apart from meeting a range of criteria for use as a bedding material, using gypsum will reduce the amount of construction waste going to landfill. A trial to simulate gypsum use in animal housing was established using an application rate of gypsum of 20 g/l; 40 g/l and 80 g/l to slurry over an eight week period. Levels of gases in the headspace of the barrels were monitored each week prior to slurry addition. Ammonia levels were lower above the slurry/gypsum mix than in the slurry alone with 34% reduction in the total ammonia loading over the eight week trial. Hydrogen sulphide (H2S) was not detected in the headspace of any barrels but after stirring, the level of H2S exceeded the detection limit of the gas meter in most of the test barrels and at a lower level in the control barrels. This pilot indicated the potential for gypsum to be used in reducing ammonia pollution from agriculture. However, its use will increase the H2S concentration in slurry. While further on-farm trials are required to confirm the findings of this study, the increased release of noxious gases is likely to be a major barrier to the uptake of this recycling route.